In the 1967 case Serio v. United States, the Supreme Court examined whether a defendant's right to counsel was violated when his attorney failed to object to an allegedly prejudicial remark made by a prosecutor during closing arguments. The defendant, Joseph Serio, had been convicted of bank robbery and appealed on the grounds that his lawyer's failure constituted ineffective assistance of counsel. However, the Supreme Court disagreed with this argument. It held that while it is generally improper for prosecutors to make personal attacks or inflammatory remarks about defendants in their summations, not every such comment will necessarily result in prejudice sufficient enough to warrant reversal of a conviction. In this particular case, even if defense counsel should have objected at trial (which was debatable), any potential harm from the prosecutor’s comments would likely have been cured by instructions given by trial judge reminding jurors they were only supposed to consider evidence presented during trial proceedings.

In the dissenting opinion for Serio v. United States, it was argued that the majority's decision to uphold Serio's conviction under a federal law prohibiting interstate transportation of stolen vehicles was incorrect. The dissenting justices believed that there wasn't sufficient evidence to prove beyond reasonable doubt that Serio knew the car he transported across state lines had been stolen, which is a necessary element of the crime under this particular statute. They pointed out inconsistencies and weaknesses in testimony from government witnesses, including one who admitted lying during initial investigations. Furthermore, they disagreed with how lower courts interpreted certain circumstantial evidence against Serio as indicative of guilt rather than mere suspicion or possibility. Therefore, they felt his conviction should be overturned due to lack of proof regarding his knowledge about the vehicle’s status at time of transport.